Defect structure and thermochemistry of YBaCo2O6-δ

The defect structure analysis of the oxygen deficient YBaCo2O6-delta double perovskite cobaltite confirms that the model proposed earlier for RBaCo2O6-delta (R - Pr, Gd, La) holds also for YBaCo2O6-delta. In particular, a good agreement between the pO(2)(T, delta) model function and experimental pO(2) - T - delta data is obtained for this oxide. By means of high-temperature drop calorimetry, the enthalpy increments of YBaCo2O6-delta samples with different initial oxygen contents (0.67 <= delta <= 1) were measured in air in the (1123-1273) K temperature range. The results obtained for YBaCo2O5.0 were fitted using a Maier-Kelley function. The smoothed values of Delta H-T(298.15)degrees, C-p(T), and Delta S-T(298.15)degrees were calculated for thermodynamically stable YBaCo2O5.0 in the temperature range 1150 <= T, K <= 1350. The drop calorimetric results for the metastable YBaCo2O5.33 were used to evaluate the standard enthalpy of its reduction at 298.15 K, Delta H-red degrees, as (161 +/- 15) kJ.(mol O-2)(-1) (expanded uncertainty with approximate to 0.95 level of confidence), which is significantly less endothermic than Delta H-red degrees of some other double perovskite cobaltites, RBaCo2O6-delta (R - Pr, Gd), within similar oxygen nonstoichiometry ranges (0.5 <= delta <= 1.0).

Automated summary

The defect structure analysis of the oxygen deficient YBaCo2O6-delta double perovskite cobaltite is in agreement with the model proposed for other double perovskite cobaltites. High-temperature drop calorimetry was used to measure enthalpy increments of samples with different initial oxygen contents, leading to the determination of thermodynamic properties such as standard enthalpy of reduction. The results for YBaCo2O5.0 show a significantly less endothermic behavior compared to other double perovskite cobaltites.